1. Field of the Invention
This invention relates to coating of gas-assisted injection molded articles and, more particularly, to a gas-assisted injection molded article suitable for plating and to a plating process for a gas-assisted injection molded article.
2. Description of Related Art
Plastic molded articles have been produced by a process known as gas-assisted injection molding. In this process, molten thermoplastic material is forced from an injection molding machine through a sprue to a plastic flow channel or runner and ultimately into the mold cavity of a mold. A gas injection nozzle is mounted in the plastic flow channel or the mold cavity to inject pressurized fluid or gas into the flow of molten thermoplastic material. The pressurized gas forces the flow of molten thermoplastic material to the far reaches of the mold cavity and results in the creation of an article which is at least hollow in part.
In producing gas-assisted molded articles such as automobile molded trim articles, a gas injection stud extends perpendicular to the main body of the molded article and provides the flow path between the plastic flow channel and the mold cavity. When the molded article is removed from the mold cavity, the gas injection stud extends outwardly from the hollow molded article. The gas injection stud is hollow and is in fluid communication with the hollow interior of the molded article. In addition, the gas injection stud has formed in the sidewall thereof an aperture through which pressurized gas is conveyed to the interior of the article during the molding process. The trim pieces are plated which requires immersion in a plating bath and a rinse bath. If the gas injection stud aperture is not plugged prior to submersion, the liquid plating solution would enter the hollow interior of the molded article through the hollow stud and the aperture formed in the stud. The plating solution within the article can leak from the article during subsequent operations and contaminate rinse baths or even corrode the painted surface of the vehicle to which the trim piece is mounted. Therefore, it is desirable to seal the aperture in the stud prior to any plating or painting operations to which the molded articles are subjected. After the molded article has been painted or plated, then the stud can be broken off and discarded.
One solution to the problem of sealing the gas injection stud has been to frictionally mount a plastic cap on the end of the stud. Unfortunately, it is not uncommon for these caps to fall off or be inadvertently removed during handling prior to the plating operation. Therefore, these caps have proved to be an inadequate solution to the problem of sealing the gas injection stud aperture during plating and painting operations.